Abstract:

An improved geothermal system for heating and cooling a building includes
a fluid loop installed in the ground with opposite ends connected to a
heat pump or other heat exchanger. The fluid loop comprises a plastic
pipe embedded with heat transfer particles. The pipe is a thermoplastic
or thermoset elastomer modified polymer having a modulus of elasticity
less than 200,000 psi.

Claims:

1. An improved geothermal pipe for heating and cooling building
structures, comprising:a plastic pipe embedded with heat transfer
particulates; andthe pipe having a modulus of elasticity less than
200,000 psi.

8. A method of geothermally heating and cooling a building,
comprising:installing in the ground a plastic pipe embedded with heat
transfer particles, the pipe having opposite ends;connecting the ends of
the pipe to a heating and cooling system of the building; andflowing a
heat transfer fluid through the pipe so as to exchange heat between the
building and the ground.

9. The method of claim 8 wherein the particulates are selected from a
group consisting of metals, metallic oxide, non-oxides, and graphite.

10. The method of claim 8 wherein the plastic pipe is selected from a
group consisting of an olefin based polymer, TPU, COPE, COPA, PVC and
SBC.

11. The method of claim 8 wherein the plastic pipe is a thermoplastic or
thermoset elastomer.

12. The method of claim 8 wherein the elastomer is selected from a group
consisting of TPO. TPV, SBC, TPU, COPA, and COPE.

13. The method of claim 8 wherein the pipe is oriented substantially
horizontally or vertically in the ground.

14. An improved geothermal system for heating and cooling a building,
comprising:a heating and cooling assembly for the building;a fluid loop
extending in the ground outside the building and having opposite ends
connected to the assembly to transfer heat between the interior of the
building and the ground;the loop including a plastic pipe having embedded
heat transfer particles.

15. The system of claim 14 wherein the pipe has a modulus of elasticity
less than 200,000 psi.

16. The system of claim 14 wherein the plastic pipe includes a
thermoplastic elastomer.

17. The improved geothermal pipe of claim 16 further comprising an
elastomer selected from a group consisting of TPO, TPV, SBC, TPU, COPA,
and COPE.

18. The improved geothermal pipe of claim 14 wherein the plastic pipe is
selected from a group consisting of an olefin based polymer, TPU, COPE,
COPA, PVC and SBC.

19. The improved geothermal pipe of claim 14 wherein the particulates are
selected from a group consisting of metals, metallic oxide, non-oxides,
and graphite.

20. The improved geothermal pipe of claim 14 wherein the plastic pipe
includes a preservative layer.

[0002]Geothermal heating and cooling have been well-known for many years.
Geothermal heating and cooling takes advantage of the relatively moderate
ground temperatures about 4 to 8 feet below the earth surface. A
conventional closed loop geothermal system circulates a water-based
solution through pipes buried in the ground.

[0003]The most common closed loop geothermal systems utilize vertical or
horizontal closed loops. A vertical loop system is used mainly when land
area is limited, with vertical bores drilled into the ground to a depth
of 150-300 feet, with the pipe loops residing in the vertical bores. A
horizontal loop system is commonly used when there is more open land,
wherein trenches are dug 6 to 8 feet deep, and coils of pipe laid in the
bottom of the trenches, which are then backfilled. The pipe coils in the
horizontal loop system may be concentric or serpentine. Another variation
is slinky-type loops which overlap one another, and thereby minimize the
trench area. A pond loop geothermal system is an alternative to the
vertical or horizontal loop systems. In the pond loop system, the pipes
are anchored in a body of water at a depth of 8-10 feet, with
approximately 300-500 feet of pipe coils.

[0004]Pipes for a horizontal geothermal system are generally easier and
less expensive to install than a vertical system. Drilling of vertical
bores is generally more expensive than trenching for horizontal loops.
However, the horizontal loops require longer length of pipe due to the
seasonal variations in the soil temperature and moisture content.
Therefore, a larger area is normally required for horizontal geothermal
pipes than for vertical pipes.

[0005]Geothermal systems conserve natural resources and energy by
providing climate control very efficiently, thus lowering emissions.
Since the heat is extracted from the earth, no fossil fuels are burned to
generate heat. Geothermal systems normally are more efficient than
propane and natural gas heating systems. Geothermal systems also minimize
ozone layer destruction by using sealed refrigeration systems. Because
these geothermal systems move heat to and from the earth, rather than
burning fossil fuels, geothermal systems reduce the amount of toxic
emissions in the atmosphere. The geothermal systems use the earth as both
a heat source and a heat sink. Since these systems do not rely on outside
air, the inside air of buildings is kept cleaner and free from pollens,
outdoor pollutants, mold spores, and other allergens.

[0006]In the heating mode, the water or fluid (typically water mixed with
an antifreeze solution, such as propylene glycol or methyl alcohol)
circulating in the earth pipe loop is colder than the surrounding ground.
This temperature differential causes the liquid to absorb energy from the
earth, in the form of heat. The water carries this energy to the heat
exchanger of the building heat pump, wherein refrigerant absorbs the heat
energy from the liquid, which then leaves the heat exchanger at a colder
temperature and circulates through the earth loop to pick up additional
energy.

[0007]The refrigerant, which contains energy from the liquid, flows from
the heat exchanger to a compressor, wherein the refrigerant temperature
is increased to approximately 160° F. From the compressor, the
super heated refrigerant travels to the air heat exchanger, wherein the
heat pumps blower circulates air across an air coil, increasing the
temperature of the air, which is blown through duct work to heat the
house or building. After the refrigerant releases its heat energy to the
air, the refrigerant flows back to the heat exchanger to start the cycle
again.

[0008]The cooling mode operates in reverse from the heating mode. In the
cooling mode, the liquid circulating in the earth pipe loop is warmer
than the surrounding ground, thereby causing the water to release energy,
in the form of heat, into the earth. The cooled liquid then flows to the
heat exchanger in the heat pump, wherein hot refrigerant gas from the
compressor releases its heat into the liquid, so as to increase the
liquid temperature, which is again released to the ground through the
earth loop. The refrigerant, which has released its heat energy to the
liquid so as to become cooler, flows to the heat exchanger when the heat
pump blower circulates warm, humid air from the building across the cold
air coil. The air is then blown through the duct work to cool the
building. The refrigerant in the air coil picks up the heat from the air,
and flows to the compressor. The refrigerant flows from the compressor to
the earth loop heat exchanger to start the cycle again.

[0009]While geothermal systems are more energy efficient than conventional
fossil fuel heating systems, the initial installation of geothermal
systems is more expensive than conventional systems due to the cost of
the pipe and the cost of equipment and labor for installing the pipe.
Vertical geothermal systems are more expensive than horizontal systems,
since drilling is costlier than trenching. However, horizontal geothermal
systems require substantial open areas to lay the pipe coils.

[0010]Therefore, a primary objective of the present invention is the
provision of an improved geothermal pipe with increased thermal
conductivity to minimize the length of pipe used in geothermal systems.

[0011]A further objective of the present invention is the provision of an
improved geothermal pipe made of plastic embedded with heat transfer
particulates.

[0012]Another objective of the present invention is the provision of an
improved thermal conductivity pipe for geothermal applications which has
a sufficiently low modulus of elasticity to allow coiling and uncoiling
of the pipe.

[0013]Another objective of the present invention is the provision of an
improved geothermal pipe made of thermoplastic or thermoset elastomer
modified polymer.

[0014]Still another objective of the present invention is the provision of
an improved geothermal pipe having metal, metallic oxide, non-ixide,
graphite, or other thermally conductive particles embedded in the pipe.

[0015]A further objective of the present invention is the provision of an
improved geothermal pipe made of an olefin based polymer (such as HDPE,
PP, LLDPE, TPO, XLPE), TPU, COPE, COPA, PVC, or SVC, or a blend or alloy
of these polymers.

[0016]Still another objective of the present invention is the provision of
an extruded, single wall or multi-layer geothermal pipe having heat
transfer particles therein.

[0017]A further objective of the present invention is the provision of an
improved geothermal pipe with heat transfer particles and having
increased flexibility and ductility.

[0018]Yet another objective of the present invention is the provision of
an improved geothermal pipe which minimizes the length of pipe required
for efficient heating and cooling of a building.

[0019]Another objective of the present invention is the provision of an
improved geothermal pipe which allows for a smaller installation
footprint as compared to standard geothermal pipe.

[0020]Another objective of the present invention is the provision of an
improved geothermal pipe which allows for shallower vertical bores as
compared to standard geothermal pipe.

[0021]A further objective of the present invention is the provision of an
improved geothermal pipe which has lower installation costs than
conventional geothermal systems.

[0022]A further objective of the present invention is the provision of an
improved geothermal pipe which is easy to handle in cold weather
conditions.

[0023]Yet another objective of the present invention is the provision of
an improved geothermal pipe which has passive gain due to higher thermal
mass of thermally conductive compounds.

[0024]Another objective of the present invention is the provision of an
improved geothermal elastomeric polymer pipe with thermally conductive
additives and a modulus of elasticity less than 200,000 psi.

[0025]Still another objective of the present invention is the provision of
an improved geothermal pipe having thermal conductivity greater than 0.5
watts per meter degree K.

[0026]These, and other objectives, will become apparent from the following
description of the invention.

SUMMARY OF THE INVENTION

[0027]The present invention is directed towards an improved plastic pipe
for geothermal heating and cooling. The pipe is an elastomer modified
polymer having thermally conductive particles embedded therein. The
particles constitute 30-70% of the pipe, by volume, or 40-90%, by weight.
This improved geothermal pipe has a modulus of elasticity less than
200,000 psi. The enhanced thermal conductivity of the pipe allows a
shorter length of pipe to be used, with enhanced heat transfer between
the fluid in the pipe and ground, as compared to conventional geothermic
pipes. The improved heat transfer minimizes the field for the geothermal
system. The pipe can be used in both horizontal and vertical systems. The
reduced pipe length reduces installation costs and increases installation
versatility.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]FIG. 1 is a schematic view showing the heating cycle for a
geothermal system.

[0029]FIG. 2 is a schematic view showing the cooling cycle for a
geothermal system.

[0032]The present invention is directed towards an improved geothermal
pipe having increased thermal conductivity with a low modulus of
elasticity. The pipe is made of plastic embedded with heat transfer
particles. The particles may be metallic oxide, non-oxides, graphite, or
other similar materials which are thermally conductive. The heat transfer
particles are preferably 30-70% by volume. Alternatively, the particles
may be in the range of 50-90% by weight for metallic oxide, and 40-70% by
weight for graphite.

[0033]The pipe may be a thermoplastic or thermoset elastomer modified
polymer. The pipe preferably is made of plastic, such as HDPE, PP, LLDPE,
XLPE, TPU, COPE, PVC and SBC, or a blend or alloy of these polymers. The
pipe may include a preservative layer, so that the pipe is resistant to
degradation from light, chemicals, and other adverse materials. The layer
may be co-extruded or mono-extruded so as to form a multi-layer pipe
extrusion. The pipe of the present invention may be a single walled
extrusion or a multi-layer co-extrusion.

[0034]The pipe of the present invention, due to modifications to improve
thermal conductivity, will approximate ASTM standard D-3035 (the standard
for conventional geothermal pipe). The pipe has sufficient strength to
prevent bursting from interior pressure or crushing from exterior
pressure. The pipe is suitable for cold weather installation, due to
increased flexibility and ductility. The pipe may be used for both
vertical and horizontal installations, though is primarily intended for
horizontal installations so as to avoid the extra cost of drilling
vertical bore holes. The increased thermal conductivity of the pipe
minimizes the length of pipe required in horizontal applications, and
thereby minimizes the trenching area. The pipe of the present invention
can also be utilized in under water installations, while minimizing pipe
length.

[0035]Preferably, the modulus of elasticity for the geothermal pipe of the
present invention is less than 200,000 psi. The thermally conductive
particulates embedded in the pipe are preferably 50%-90% by weight.

[0036]Normally, thermally conductive additives increase the modulus of
elasticity. Such stiffness makes the pipe difficult to handle, including
coiling and uncoiling. To overcome such stiffness, the present invention
utilizes an elastomer polymer modified so as to maintain flexibility of
the pipe. The elastomer may be TPV, SBC, TPO, COPE, or other known
elastomeric material. This addition of the low modulus elastomer offsets
the increase in modulus caused by the addition of the thermally
conductive particulates.

[0037]For example, the polymer may be in the range of 1-50% by weight, and
the elastomer may also be in the range of 1-50% by weight. Alternatively,
both the polymer and elastomer are preferably in the range of 1-70% by
volume.

[0038]With the present invention, the geothermal installation will use
less than half the length of pipe with twice the heat transfer, as
compared to conventional geothermal pipe. With the improved geothermal
pipe, one third the conventional length of pipe can be used and still
achieve the same heat transfer result. Therefore, the size of the
horizontal field can be minimized.

[0040]Table 1 below is a comparison of standard or conventional HDPE
geothermal pipe properties versus two embodiments of pipe according to
the present invention (Green Geo Soft and Green Geo Rigid). Thus, the
pipe can be tailored or custom manufactured for specific strength and
stiffness. The soft and rigid pipe embodiments differ, depending up on
the amount of rubber in the pipe. Both the soft (low modulus) and rigid
(high modulus) pipe have higher thermal conductivity than the
conventional HDPE pipe. The low modulus Green Geo soft pipe has the
following composition:

[0050]Ideally, the geothermal pipe has a thermal conductivity which
matches or approaches that of the soil in which it is embedded. Table 2
shows a comparison of the conductivity for standard PP and HDPE pipe, as
compared to the Green Geo pipe of the present invention and various types
of soil.

[0051]Tables 3-5 show a comparison of the temperature differentials of 700
feet of standard HDPE pipe with a slinky installation at 6 foot depth
versus 320 feet of the Green Geo soft, low modulus pipe of the present
invention installed in a slinky pattern at 6 feet depth. These tables
show the temperature of the fluid coming into the manifold and out of the
manifold over the course of seven months from February-August 2009.
During the first month of testing, the soil had not yet compacted, such
that intimate contact with the installed pipe was not maximized. The pipe
and soil contact improved following the Spring thaw and rain.

[0052]It is further noted that the manufacturer of conventional HDPE
produces approximately 2.0 pounds of carbon dioxide per pound of HDPE.
Since Applicant's improved geothermal pipe allows for shorter lengths,
less CO2 is produced during the manufacture of the pipe.

[0053]Also, in vertical installations using improved geothermal pipe of
the present invention, the improved conductivity allows for substantially
shorter length of pipe, and thus shallower bores which avoid potential
ground water contamination concerns. For example, with Applicant's pipe,
vertical bores of only 10 feet may be utilized, as compared to 200 foot
deep bores for conventional vertical geothermal installations.

[0054]With respect to the drawings, a geothermal heating and cooling
system is generally designated by the reference numeral 10. The system 10
includes the improved pipe 12 of the present invention. While the
drawings show the pipe 12 installed horizontally in the ground, it is
understood that the pipe 12 may also be installed in vertical bores in
the ground. The opposite ends of the pipe 12 are connected to a heat pump
or other fluid heat exchanger 14 for the building 16 so as to form a
loop. The pipe 12 may be oriented in any convenient configuration,
depending on the available ground space, and obstacles such as trees. The
building 16 may be residential or commercial. The geothermal system 10
also includes a compressor 18, an expansion valve 20, and an air heat
exchanger 22.

[0055]As seen in FIGS. 1 and 2, the fluid in the pipe 12 flows in the
direction as indicated by the arrows 24. The fluid in the internal loop
26 connecting the heat pump or water heat exchanger 14, compressor 18,
air heat exchanger 22 and extension valve 20 flows in a first direction
for heating, as shown by arrows 28 in FIG. 1, and in the opposite
direction for cooling, as shown by arrows 30 in FIG. 2.

[0056]The invention has been shown and described above with the preferred
embodiments, and it is understood that many modifications, substitutions,
and additions may be made which are within the intended spirit and scope
of the invention. From the foregoing, it can be seen that the present
invention accomplishes at least all of its stated objectives.